The present invention relates generally to an apparatus used for aiding in the transport of payloads from the Earth""s surface to outer space. Specifically, the present invention relates to a reusable flyback booster that incorporates a removable rocket propulsion module within an airframe. Still more specifically, the present invention relates to a reusable flyback booster comprising an aircraft, having air breathing engines and capable of landing on a runway, said aircraft functionally enclosing a separate launch vehicle stage. The present invention may be used as the first stage of a multistage launch vehicle. Thus the present invention also relates to a comprehensive launch vehicle system architecture wherein the stage used in the flyback booster and the upper stages are selected to cost optimize the multistage launch vehicle for launch of a specific payload or class of payloads.
The present invention""s background art is generally found in the art of space launch vehicles. Patents in this field of art are classified generally in international class B64G and in U.S. class 244.
The inventors identify the following background art because they believe it will be useful in understanding, searching, and examining the invention. This invention lies in an area of the technical arts where it really is necessary to be a rocket scientist to understand the invention. The inventors anticipate that they may be required to explain the invention to persons who are not technically trained, such as administrators, jurists or judges. To aid in understanding the present inventors they offer: 1. an overview of information on space launch vehicles, including some technical and cost data on certain specific vehicles; 2. information on the background art related to partially reusable launch systems and 3. relevant U.S. patents. Taken as a whole, this body of information represents the current state of the art in launch vehicle recoverable boosters, as the inventors know it at the time of their filing of this patent application. It also illustrates the enormous complexity of this field of art, which is currently in a dynamic period of development.
Although sounding rockets may reach altitudes above the atmosphere of the Earth, the term space launch vehicle is applied usually to those rocket boosters designed to place satellites in orbit or to impart Earth-escape velocity to spacecraft.
By about 1950 the technology of rocket propulsion had reached a level at which consideration of a project to launch an Earth satellite became feasible. Worldwide scientific studies during the IGY of 1957-58 provided the basis for funding. In 1955 both the United States and the Soviet Union announced satellite programs as part of their national effort in the IGY.
When Sputnik 1 and 2 were launched in 1957 the Soviet Union released no details of their launch vehicles. In May 1958 Sputnik 3, weighing nearly 1,360 kilograms, was launched. It was not until 1967 that the basic Soviet launch vehicle was displayed. It was a 2xc2xd-stage vehicle of the xe2x80x9cAxe2x80x9d series (in this case, xe2x80x9cA-1xe2x80x9d): two stages with four drop-away booster pods. Each booster pod contained four rocket engines (totaling 16) with propellant tankage, and the central core had four engines. Propellants were liquid oxygen and kerosene.
The United States launched its early satellites with two different vehicles, the Jupiter-C and Vanguard. Jupiter-C was a modified Redstone liquid-propellant ballistic weapon of medium range to which were added more tankage length and three upper stages of clustered solid-propellant rockets. The modification was originally designed to achieve a velocity of six kilometers per second to test a nose cone (reentry vehicle). The desired velocity was obtained with two upper stages, one a cluster of four solid-propellant rockets and the other a single rocket. By increasing the final velocity 1.5 kilometers per second to the required 7.5 kilometers per second, satellite velocity could be obtained for a small scientific payload. The additional velocity was obtained by adding another stage with a cluster of solid-propellant rockets so that the upper stages consisted of 11, three, and finally one rocket carrying a payload weighing 8.2 kilograms. In 1954 the Army Ballistic Missile Agency and the Office of Naval Research jointly proposed this scheme, known as Project Orbiter, but a newly designed Vanguard launch vehicle was selected. Failures in early attempts to launch Vanguard, however, resulted in eventual approval of the Project Orbiter approach. Thus the first U.S. satellite, Explorer 1, was launched by a Jupiter-C on Jan. 31, 1958.
The Vanguard launch vehicle was a three-stage booster approximately equal in length (about 22 meters) to the Jupiter-C but much lighter in takeoff weight (10,250 kilograms compared to 29,000 kilograms). Vanguard launched its first satellite (1.4 kilograms) into high orbit on Mar. 17. 1958. After a few more flights, the Jupiter-C was retired in 1958 and the Vanguard in 1959.
During the 1960s the United States developed a series of standard launch vehicles. The Air Force modified a Titan II intercontinental ballistic missile (ICBM) for space launch purposes by strapping two solid-propellant booster rockets, three meters in diameter, to the liquid-propellant core vehicle. The Titan IIIC was used for large military satellites. Then NASA increased performance of the obsolete Thor intermediate-range ballistic missile (IRBM) by adding solid-propellant boosters. A liquid oxygen/liquid hydrogen upper stage, Centaur, was used on obsolete Atlas and Titan ICBMs to launch large spacecraft.
The Saturn series of NASA launch vehicles was developed specifically for the Apollo lunar mission program. The two operational Saturn models were the two-stage Saturn IB and three-stage Saturn V. The Saturn IB was used for Earth orbital developmental missions of Apollo, while the Saturn V was employed for lunar missions. Saturn V stood 110.6 meters high and weighed over 2,700,000 kilograms at launch. It could place 104,000 kilograms in orbit and send 45,000 kilograms to escape velocity.
For some years the launching of spacecraft was limited to the United States and the Soviet Union. The reason was that the early rocket-powered launch vehicles were based on long-range ballistic missiles, which only these countries had developed. France was the third nation to launch a satellite (1965), followed by Japan (1970), the People""s Republic of China (1970), and the United Kingdom (1971). Under the auspices of the European Space Agency (ESA), the nations of Western Europe developed the Ariane expendable launcher during the 1970s to assure themselves of independent launch capability. This action was taken, in part, in response to the U.S. refusal to guarantee flights for communications satellites that might compete with U.S. telecommunications carriers. A three-stage vehicle that burns storable and solid propellants in its first two stages and employs a cryogenic engine in its third, Ariane has become a formidable competitor for commercial space launch services, capturing about half of the global market. It is capable of launching two satellites of the U.S. Delta class (an Earth-orbit payload of 1,770 kilograms) at one time or one Atlas-Centaur-class satellite (an Earth-orbit payload of 4,670 kilograms). With the new cryogenic propellant core, Ariane is approaching payload weights that only the Shuttle can handle.
An important factor affecting space mission cost is the cost of launch vehicles. Many of the major launch vehicles are designed to place payloads of 1500-6000 kg into geostationary transfer orbit, at a typical cost of $50M-150M. Such launch performance is to little and costs are far too high for the low-cost missions satellite operators require.
Many of the early Western space launchers had, by modern standards, very small payloads. The U.S. Vanguard rocket could place 20 kg into LEO, whilst the French Diamant and British Black Arrow both had LEO capabilities of approx 50 kg. From the mid-1960s onwards launcher development concentrated on increasing payload weight, but during the 1980s the growing interest in small satellite development lead to a number of small and (relatively) low-cost launchers being produced. A further source of small launchers opened up in the late 1980s with the decommissioning of many U.S. and former Soviet nuclear missiles. Russia in particular has been keen to convert former military missiles into launchers which can be sold for foreign currency.
Unless otherwise specified LEO (Low Earth Orbit) and polar orbit payload data are for a 100 nm orbit. LEO performance is generally given for the lowest inclination achievable from the vehicle""s main launch site. In some cases, sources provide performance data for non-standard orbits without explicitly saying so. This can introduce some errors into the data for less common vehicles.
GTO stands for Geostationary Transfer Orbit, and should not be confused with GEO, Geostationary Earth Orbit. The satellite or an attached apogee kick motor generally performs the impulse from GTO to GEO, so launch vehicles often specify only GTO capability.
Price and performance data may vary. Launch prices depend on the spacecraft, currency exchange rates, and market fluctuation. Payload depends on fairing and adapter selection. This data should be accurate enough to make comparisons and conduct preliminary analysis.
It is difficult to find comprehensive data for some Russian or Chinese systems since they were often secret, and data on the more obscure foreign launch systems doesn""t get published very frequently. When data is available, sources sometimes disagree. Therefore, reliability data for a few launchers may be out of date or inaccurate.
The Ariane 4 series holds the largest market share in the international commercial launch market. Development is funded by the European Space Agency and lead by CNES, the French space agency. Arianespace conducts operations. The vehicles launch from French Guiana in South America. Ariane 5 was designed to launch multiple large communications satellites for a lower cost than previous versions. However, satellites have continued to grow since the program was started almost ten years ago. There is speculation that Ariane 5 will eventually be too small to launch two satellites, but too large to launch just one. Therefore, ESA has approved a roughly $1-2 billion xe2x80x9cAriane 5 Evolutionxe2x80x9d project to increase GTO payload to about 7.4 tons in small increments after to the year 2000.
Atlas is the largest commercial launch vehicle in the U.S. and is used frequently for commercial and military launches. Starting in the summer of 1995, Atlas was marketed jointly with the Russian Proton vehicle by International Launch Services, a joint venture of Lockheed Martin and Russian aerospace companies. This offers more flexibility for customers.
The Delta launch vehicle family is built and marketed by McDonnell Douglas (now Boeing). The Delta II has proved reliable, but is too small for most geosynchronous satellites. Therefore, McDonnell Douglas is developing the Delta III, with a much larger payload. Hughes has purchased 10 launches for its satellites. New Delta versions were also designed for NASA""s Med-Lite contract, which sought launch vehicles between the size of small launchers like Pegasus, and the Delta II, which was the smallest of the large launchers. The smaller Delta versions will be used for future Mars missions, among other things
The H-2 is the first Japanese launch vehicle to be entirely developed domestically. Previous N series and H-1 vehicles used Delta components. The H-2 is designed to carry heavy payloads to orbit and has worked well so far. However, it is unlikely to be commercially attractive in the near future, due to high costs and low flight rates. NASDA hopes to cut costs by as much as 50% by the turn of the century, in part by simplifying the design and including some foreign components. The H-2 is the cornerstone of NASDA""s plans for increasing activities in space, including eventual human missions.
Kosmos (also spelled Cosmos) is a Russian vehicle comparable in size to the American OSC Taurus launch vehicle. Following back to back failures of the Pegasus XL, LLV. and Conestoga in the summer and fall of 1995, Kosmos attracted attention in the United States as an alternative launcher with a more reliable history. Several companies have worked out joint agreements with the manufacturer, Polyot. Assured Space Access appears to be the current favorite, although other companies have also been involved. Final Analysis Inc. has reserved a number of launches for its own use and is marketing extra payload space on those launches. Kosmos has reached orbit at least 389 times.
The first flight of the LLV-1 (now called Athina 1) failed during the summer of 1995 when the vehicle began pitching out of control. Fortunately, the vehicle had a good order book for such a new vehicle, including NASA""s Lewis and Clark satellites, and the Lunar Prospector mission. Therefore the LLV overcame this initial setback.
Pegasus was the first new American vehicle in more than a decade, and deserves some credit for restarting the interest in small satellites. Pegasus is a small, all solid rocket vehicle built by Orbital Sciences Corporation. The winged rocket is launched from beneath the company""s L1011 aircraft. The original Pegasus configuration is being phased out, in favor of the Pegasus XL (Extended Length). The first two Pegasus XL flights were failures.
Taurus was developed to meet military requirements for rapid launch of small spacecraft. It consists of Pegasus stages mounted atop a Castor 120 first stage.
Proton is the heavy lift workhorse of the former Soviet launch stable. It is being marketed in the west by International Launch Services, a joint venture between Krunichev and Lockheed Martin. ILS also offers the Atlas. Russia is currently limited to offering prices within 7.5% of western prices and the number of GEO launches is limited to 8 before the year 2000. However, there is speculation that these restrictions may be abandoned as Russian launches become more commercialized. ILS has twelve western contracts for Proton launches, starting in 1996 with an Astra satellite for Societe Europeenne de Satellites of Luxembourg. Proton is also scheduled to play an important role in launching space station components. Krunichev plans to offer new upper stages for Proton, including the storable propellant Breeze-M upper stage in 1998 and the OHSM cryogenic stage a few years later. Proton will put 3.2 tons in GEO with Breeze-M and 4.5 tons with OHSM. Current GEO capability is about 2.6 tons with the Block D upper stage. In addition to these technical changes. ILS is considering conducting Proton launches from Cape Canaveral, or sites in Australia or Brazil. Launching closer to the equator would increase performance.
Shavit is Israel""s first, and so far only, launch vehicle. It is derived from the Jericho II ballistic missile. Israel Aircraft Industries is developing a more advanced version with an added stage, which would be called xe2x80x9cNext.xe2x80x9d The payload of the new vehicle would be slightly higher than Pegasus, and a cost of $15 million has been suggested. Commercialization is desired because Israeli missions number less than one a year and have limited government support. In order to avoid dropping spent stages on Arab neighbors, Israel launches west over the Mediterranean, decreasing the vehicle""s performance significantly.
Titan II vehicles are left over ballistic missiles that have been refurbished for space launch. They are used for polar orbiting Earth observation systems. It was a Titan II that launched Clementine. Titan IV is used mainly for large military payloads, including Milstar communications spacecraft and classified intelligence platforms. A Titan IV is also booked to launch NASA""s Cassini mission to Saturn. Note that because all Titan IV launches are government missions, and most are classified, prices are subject to debate.
Zenit is the newest of the large former Soviet vehicles, having come online in 1985. It suffered three consecutive failures between 1990 and 1992. NPO Yuznoye manufactures Zenits in Ukraine. Boeing has a joint venture with NPO Yuznoye and the Norwegian marine engineering company Kvaemer to launch Zenits from a modified oil platform. Due to the lower launch site latitude and a new upper stage from RSC Energia, performance will increase. Payload to GTO will increase to about 5400 kg. Payload to LEO will be about 13.000 kg.
X-34 (United States)
X-34 is a semi-reusable vehicle. Its development was funded in part by a $70 million contract with NASA. OSC, which spent a total of $100 million on the project, manage the project. Plans are for the vehicle to be carried atop a NASA 747 shuttle transporter and launched at altitude. The vehicle would reach roughly half of orbital velocity and eject a satellite with an expendable upper stage to reach orbit. Estimated price is around $4 million per launch.
EELVxe2x80x94Evolved Expendable Launch Vehicle (United States)
The U.S. Air Force has the responsibility for funding development of U.S. government ELV programs; EELV is their answer. The Air Force has provided about $1 billion to Boeing and Lockheed Martin each of them to develop a new launch vehicle that can launch all military spacecraft. Theoretically, the consolidation would mean high flight rates for these two launch vehicle types, thus lowering unit costs. These two vehicles are currently under active development.
A number of small space launch vehicles that could be used with the present invention are in planning and development. These include:
ESA/CNES Small Launchers (Europe)
ESA and the French space agency CNES have considered all manner of small launchers, be they solid or liquid, air launched or ground launched. Proposals have included derivatives of Ariane, various national missile programs, or Russian vehicles like Soyuz. The current study project is the European Small Launcher (ESL), an all solid vehicle which could launch one ton into a 700 km sun-synchronous orbit for $20 million.
Italian Small Launchers (Italy)
A variety of small launch vehicles have been studied and tested by the Italian space agency, University of Rome, and Italian aerospace firms. Generally the vehicles are derived from Scout components, since Italy has experience launching Scout rockets from their San Marco platform off the coast of Kenya. Various projects have gone by the names Vega, Zefiro, San Marco Scout, Advanced Scout, etc.
Kistler K-1 (United States)
Kistler is an aerospace company, which is using private funds to develop an all reusable, two stage small launch vehicle. Tests of hardware for the K-0, a subscale engineering test vehicle, have been conducted. The Kistler fleet would include the K-1, with a payload of 2000 pounds to LEO starting around the turn of the century, and the K-2 which would carry 6000 pounds a starting a few years later. Eventually, Kistler would like to build the K-3, which could launch 20,000 lbs. The company is releasing little public information, and management and engineering shakeups have been occurring, which could affect the design and timeline for the fleet. For more information, see the Kistler homepage at http://www.newspace.com/Industry/Kistler/home.html.
PacAstro (United States)
PacAstro now has at least three contracts; customers include KITcom of Australia which plans to launch satellites similar to Orbcomm, and the Swedish Space Corp. Much of the technology will be developed under contract with U.S. Air Force for a sounding rocket dubbed PA-X. The PA-2 would carry 340 kg (750 lbs) to LEO or 225 kg (500 lbs) to a polar orbit for $6 million dollars
Rockot (Russia/Germany)
Rokot is a three stage liquid propellant launch system developed in Russia and funded in part by German companies. Eurockot Launch Services GmbH will market it. Rockot is derived from the SS-19 ICBM with an additional upper stage, and should be able to put about 1800 kg into low orbits.
Russian Small Launchers (Russia):
A large number of new small launch vehicles are being designed in Russia. They are usually derived from ICBMs or SLBMs. They include:
Riksha-1: Under development at NPO Energomash, to launch 1.7 tons to LEO for $10 million.
Surf: Sea-launched vehicle derived from the SSN-23 and SSN-20 submarine ballistic missiles.
Space Clipper: Air launched version of SS-24. This is a Ukraine venture. The manufacturer is NPO Yuzhone.
Seagull (Russia/Australia)
Russian organizations and the Australian Space Office are discussing a project to co-produce a liquid-fueled space launcher with a capacity of about one ton into low orbit. The vehicle would be a new design, though it would use a number of existing components. Launch would take place either from Woomera or a site on the northeast coast of Australia.
VLS (Brazil)
The VLS has been a long standing goal of the Agencia Espacial Brasileria and a major part of the Brazilian Complete Space Misson (MECB). The launcher is derived from the Sonda IV sounding rocket and is currently designed to put 185 kg into a 750 km orbit.
Reusable Launchers
A frequently-proposed solution to the high cost of access to space is the development of reusable launch vehicles. It has often been pointed out that if aircraft were built for every flight and scrapped thereafter, then air travel would be as expensive as space launch. Unfortunately the economic as well as technical challenges involved in building a reusable launch vehicle (RLV) are considerable, as is evident from the continued use of expendable launchers some 40 years after the launch of the first artificial satellite. The one operational launch vehicle with any degree of reusability the U.S. Space Shuttle, is as expensive to operate in terms of $/kg to LEO as most expendable launchers and requires a large support operation to refurbish each Orbiter after flight. The main difficulty with building a fully reusable launch vehicle, particularly one which is a single unit, is that of achieving orbital velocity (9,500 m/s including drag and gravity losses) without using disposable stages or tanks.
xe2x80x9cIspxe2x80x9d the abbreviation for is a quantity known as the specific impulse of the particular propellant combination and rocket engine being used. Specific impulse is measured in units of pounds force per pounds mass per second, frequently shortened to xe2x80x9csecondsxe2x80x9d. Commonly used propellants have values of Isp between 260s and 450s; to achieve a final velocity of 9,100 m/s with them would require a mass ratio of 8 to 35. Mass ratios much above 7.3 are very difficult to achieve, especially with any significant payload, using those propellants with sufficiently high Isp to allow lower mass ratios: liquid hydrogen as a fuel is low-density, leading to difficulty in building large tankage while maintaining the required mass ratio. Also, to maintain a reasonable level of acceleration at lift off, a launcher must carry heavy rocket engines that significantly vary its thrust during its burn. Expendable launchers drop off structure such as empty tanks and the large engines needed for takeoff, thus maintaining their effective mass ratio and lowering thrust throughout flight. Building an RLV as a single unit is thus an exceedingly difficult proposition.
In recent years, advances in materials technology have given rise to the hope that it may be barely possible to build a single-stage-to-orbit (SSTO) RLV. By using strong but light materials such as composites and advanced alloys it may be possible to build a vehicle light enough in relation to its size that it""s mass ratio is high enough to achieve orbit with a useful payload. The NASA/Lockheed-Martin X-33 is being built as a technology demonstrator for such a vehicle, and should carry out suborbital flights in late 1999 or 2000. It is hoped by NASA that such work will lead to the commercial development of operational SSTO-RLVs within the next 10 years. An objective of such research is to develop an RLV that can be refurbished between flights with little more than the routine servicing required by conventional aircraft. Progress was made in this area by the McDonnell-Douglas DC-X/XA before it was lost in a flight accident, with successful demonstration of rapid turnaround by a small flight crew. If it is successful, this research could lead to an RLV that can fly at short notice (under a week) to deliver to orbit a payload at relatively low cost (under $1000/kg to LEO). Such a vehicle would be ideal as a launcher for rapid-response missions, as it would make it feasible to procure a dedicated launch into a specific parking orbit at short notice and at reasonable cost. However, as mentioned, it is unlikely that such a vehicle will enter operational service before 2007, with 2010-2015 or beyond being more likely. As such, whilst the launch of rapid-response missions is likely to become a much easier proposition with the development of SSTO-RLVs, this will not happen in the near future. Very low payload fractions and high risk and development costs of SSTO vehicles make many experts believe that they will never by a cost-effective means of launching significant payloads.
However, the SSTO-RLV is not the only approach to low-cost space access. Making any element of an ELV reusable should reduce costs. This is only true, however, so long as the element in question actually is easy to refurbish, and the cost of developing such a capability is not excessive. The U.S. Space Shuttle, for instance, reuses all elements except its external fuel tank. However, the high development cost and the effort involved in refurbishment between flights results in its cost to orbit being as high as most expendable launchers. Such savings are likely to be more pronounced if the part reused is the largest component, i.e. the first stage. The first stage is a particularly promising candidate for replacement, as not only does it have to carry the payload and upper stages, but it must overcome the most significant delta-V overheads (atmospheric/gravity drag) associated with launch. These overheads typically add 150-2,000 m/s to the delta-V required to reach normal LEO orbital velocity of 7,800 m/s. Even small improvements in this area can bring dramatic benefits. A good example is the Orbital Sciences Corporation (OSC) Pegasus air-launched rocket, which uses a converted L-1011 airliner as a reusable xe2x80x98zeroth stagexe2x80x99. Even by taking the remaining stages to just 9,000 meters altitude and 250 m/s velocity, the required mass of a Pegasus rocket is approximately halved in takeoff weight from a ground-launched version of equivalent performance. An additional factor in making just the first stage reusable is that its recovery is much easier than for an SSTO. An SSTO returning from orbit must cope with re-entry at approximately Mach 25, whereas a reusable first stage would reach a peak velocity of Mach 3 to Mach 6.
A number of partly reusable launch vehicles (PRLV) have been proposed around the concept of a reusable first stagexe2x80x94often air-launched in some wayxe2x80x94being used to boost the payload and upper stages onto a suborbital trajectory. During 1995 OSC carried out development work on the X-34, effectively a reusable vehicle that replaced the first stage of Pegasus. Although the X-34 has been redesigned as a suborbital test vehicle, other companies have made similar proposals. Kelly Space has begun development work on the Eclipse winged launcher that would be towed behind an airliner before climbing on rocket power into a trajectory where solid-propellant upper stages and the payload would be released from a cargo bay. Pioneer Rocketplane""s xe2x80x98Pathfinderxe2x80x99 (originated as the U.S. Air Force xe2x80x98Black Horsexe2x80x99 spaceplane study) is a small spaceplane that enhances its performance via aerial propellant transfer. It takes off on a runway using two conventional augmented turbofan engines, carrying a full load of kerosene fuel but only sufficient liquid oxygen (LOX) oxidizer to accomplish the required propellant transfer. It rendezvouses with a tanker aircraft to take on a full load of LOX before using its LOX/kerosene rocket engine to climb to 100 km altitude at a speed of Mach 12. Here it releases a solid-propellant upper stage (typically a STAR48 or -63 boost motor), which accelerates the attached payload into orbit. The Pathfinder then re-enters and relights its turbofan engines to return to base. Aerial propellant transfer allows the Pathfinder to reduce structural weight as its wings and landing gear are sized to support a much lower weight than if it took off with a full propellant load. Speculations indicate that Pathfinder should be able to place 1,000 kg into polar LEO, or more into orbits of lower inclination, for an estimated cost of $5M. Pioneer is currently carrying out a design study on the Pathfinder for NASA as a contender for the Bantam-X RLV proposal; it is also a contender for the proposed USAF space sortie vehicle.
NASA is studying the possibility of using liquid fueled fly back boosters (xe2x80x9cLFFBxe2x80x9d) as part of the U.S. National Space Transportation System, commonly called the xe2x80x9cSpace Shuttle.xe2x80x9d The LFBB is designed to be a completely reusable liquid-fueled booster that will return to the launch site, using an autonomous landing system, after separation from the Orbiter and external tank. By way of contrast, the current Shuttle SRBs have to be recovered from the ocean and then extensively refurbished for later use. The initial proposal for the LFBBs includes two options: xe2x80x9cdualxe2x80x9d boostersxe2x80x94two separate winged boosters; and xe2x80x9ccatamaranxe2x80x9d boostersxe2x80x94a dual fuselage connected by a common wing. The catamaran version has been abandoned for technical reasons. Wind tunnels tests of the LFBB shuttle configuration have been conducted. Both Boeing and Lockheed Martin have performed concept definition studies of the LFFB. This work is continuing.
1. xe2x80x9cInternational Reference Guide to Space Launch Systemsxe2x80x9d by Steven J. Isakowitz, 1991 edition. Published by AIAA.
2. xe2x80x9cTransportation Systems Data Bookxe2x80x9d NASA Marshall SFC. Revision A 1995.
3. xe2x80x9c1991-1992 Europe and Asia in Space,xe2x80x9d compiled by Nicholas Johnson and David Rodvold for USAF Phillips Lab.
4. As an additional source of information, NASA maintains a web page at http://www.ksc.nasa.gov/elv/elvpage.html which includes some information about expendable launch vehicles used by NASA.
5. xe2x80x9cCapabilities, Costs, and Constraints of Space Transportation for Planetary Missions,xe2x80x9d by Karen Poniatowski and Michael Osmolovsky of NASA HQ""s Launch Vehicle Office. This paper, along with papers on planetary capabilities of the Delta, Titan II and M-V were presented at the 1994 IAA International Conference on Low-Cost Planetary Missions, and are archived in Acta Astronautica, Vol. 35, 1995.
6. More recent information on launch vehicles may be found at www.jsc.nasa.gov/bu2/launch.html
U.S. Pat. No. 3,702,688 teaches a fully recoverable launch system consisting of two piloted winged vehicles that launched vertically in a mated configuration. A first larger booster vehicle was to have propelled the mated pair to an altitude of about 65 kilometers where the second vehicle was to be released. This system was never built.
U.S. Pat. No. 3,929,306 teaches a partially recoverable space shuttle system with rocket engines carried below an external fuel tank. The engines are recovered by loading them on board the Orbiter after their fuel is exhausted.
U.S. Pat. No. 4,557,444 teaches a dual structure SSTO aerospace vehicle having an aero shell structure and an internally disposed separable and reusable integral tank for its hydrogen fuel and its liquid oxygen.
U.S. Pat. No. 4,796,839 teaches a launch vehicle whose first stage rocket motors are ejected and recovered after first stage burnout when they by use of aeroshells and parachutes.
U.S. Pat. No. 4,834,324 teaches a space transportation system comprising several different modular units usable in a plurality of different configurations for different payloads and space missions. All units include aerodynamic devices such as fixed or swing-wings for a controlled returned to a runway landing on Earth.
U.S. Pat. No. 5,143,327 teaches a heavy lift launch vehicle having disposable fuel tanks and a plurality of winged flyback propulsion modules as a first stage.
U.S. Pat. No. 5,402,965 teaches the use of a carrier aircraft to fly a launch vehicle to a launch altitude and velocity. The significant teaching of this patent is the use of a detachable positioning apparatus that is recovered and reused from the launch vehicle.
U.S. Pat. No. 5,740,985 teaches a two-stage launch system, the first stage consisting of two flyback boosters or aircraft.
Having studied all of the prior art, the present inventors draw the following conclusions:
First, the main impediment to the development of space industry is not technical or engineering problems. It is purely economic. The high cost (now above $5,000 to $20,000 per kilogram) of launching payloads to space precludes significant development of a space industry, space tourism and the all other development of space as an ordinary venue for business and personal activities. Many econometric studies have shown that a cost reduction of at least one order of magnitude, to less than $1,000 per kilogram, will be required to make space a practical place to live and work.
Second, the greatest economic savings should come from the lowering of the costs of operating the first stage of any launch vehicle. One way to do this is to make the first stage booster reuseable. Hundreds of millions of dollars have been spent and thousands of engineers have worked for years on this problem. The original NASA proposal for the Space Shuttle included a fully reusable first stage, but was not accepted due to high development costs. This work, as, for example, on the LFBB, is continuing. Mountains of paper studies have been written on the problem. All of them require the development of entirely new rocket propulsion systems. Such novel systems are extremely expensive to design and test. The development costs of such systems have been found by past studies to largely negate the cost savings realized by the reusable booster.
Third, nothing in the prior art known to the present inventors teaches the use of an inexpensive existing booster stage as a removable propulsion module an aircraft that can function as a flyback first stage booster in a multistage launch vehicle system.
The present invention is a flyback booster comprising an airplane housing a separable rocket propulsion module. The propulsion module may be a modified existing rocket stage, such as the Zenit, Atlas III or others; or it may be a newly designed and built rocket propulsion module.
The advantages of the present invention include separation, to the maximum extent possible, of the development, procurement and maintenance of the aircraft and rocket propulsion modules. This separation is expected to result in major economies in the procurement and operations of the launch system.
The removable rocket propulsion module may be lightly constructed because the airplane fuselage carries all aerodynamic and bending loads, transmits thrust to the payload and provides protection from externally generated heat and sound pressure levels. Attachment of the module to the fuselage and transmission of thrust loads from the module to the airplane is accomplished in its aft section of the propulsion module, with lateral motion constraints only on its forward section.
The present invention has a disadvantage. It increases the dry weight of the flyback booster. This is a relatively minor matter for a first stage booster because the first stage separates from its payload at about ten percent of orbital energy. If an existing xe2x80x9coff the shelfxe2x80x9d rocket propulsion stage is used as the removable propulsion module, its modification costs will be much less than the development and test costs required to build an integral tank rocket propulsion system. The inventors believe, as a result of their mathematical model of the present invention, that use of a separable rocket propulsion module will add only about ten percent to the dry weight of the flyback booster, compared to its weight if it were to be constructed with integral tanks as is taught by the prior art.